Control device



Aug. 8, 1950 c. w. EICHHORN CONTROL DEVICE 4 Sheets-Sheet l Filed Oct.23. 1943 v QJ o Mu @I b@ Aug. 8, 1950 c. w. EICHHORN CGNTROL DEVICE 4Sheets-Sheet 2 Filed Oct. 23, 1943 Gttorneg C. W. EICHHORN Aug. 8, 1950CONTROL DEVICE Filed oct. 23, 1945 4 Sheets-Shes?l 5 ttorneg Aug- 8,1950 c. EICHHORN 2,518,129

CONTROL DEVICE Filed Oct. 23, 1943 4 Sheets-Sheet 4 Bnnentor CII/M255 W.,FICH/MEN Patented ug. 1930 CONTROL DEVICE Charles W. Eichhorn, Weston,Mass., assigner to Minneapolis-Honeywell Regulator Company, Minneapolis,Minn., a corporation of Delaware Application October 23, 1943, SerialNo. 507,462

1 Claim.

This invention relates to control devices, and more particularly to suchdevices which have for their purpose to maintain constant acharacteristic of the electrical output of a machine which is driven bya motor whose speed varies widely.

As is well known, the operation of modern aircraft, particularlymilitary craft, requires the expenditure of a considerable amount ofelectrical energy in the actuation of the various controls, indicators,communication devices, and so forth. The source of this electricalenergy is ordinarily a generator or alternator which may be self excitedor excited from the shipsbattery, and which may receive its power eitherfrom the ships en gine or from a secondary propeller, wind driven by thepassage of the craft through the air. The spe'ed of either of thesemotors varies widely, depending on the load, wind, altitude, speed ofthe craft, flying evolutions, and other conditions. Yet it is desirablethat the output of the electrical machine be maintained substantiallyconstant. The frequency, for example, of the output of an alternatorshould not be allowed to vary so far that electronic and other devicesdesigned to operate at a given frequency suffer appreciable or severediminution in efficiency.

It will be realized, of course, that the problem is not limitedexclusively to provision of electrical power in aircraft, but arises inany case when source of power whose speed varies is used to drive anelectrical machine whose output is desired to remain constant. The fieldof wind driven generators is such a field distinct from the aircraftfield.

It is therefore an object of my invention to provide an improved meansfor regulating the output of a dynamo-electric machine.

It is another object of my inventionto provide means for maintaining theoutput of a dynamoelectric machine constant in the presence of variablepower input to the machine.

A further object of my invention is to provide a means for maintainingthe frequency of the output of an alternator constant in the presence ofwide variations in the speed of the driving means.

A more specific object of my invention is to provideelectronic-hydraulic means for regulating a characteristic of the outputof a dynamoelectirc machine.

Yet another object of my invention is to provide means for maintainingthe speed of a driven shaft constant in the presence of wide variationsin the speed of a driving shaft.

Other objects and advantages of my invention will appear from a study oithe following speci- (Cl. S22-40) 2 iication, and the subjoined claim,together with the drawing which is attached hereto and which forms apart hereof, and in which:

Figure 1 is a diagrammatic showing of a system comprising one embodimentof my invention;

Figure 2 is a circuit diagram showing an organization making up apreferred embodiment of an electronic frequency responsive deviceforming an important part of my invention;

Figure 3 is an end view of a hydraulic regulator also comprising animportant part of my invention in a preferred form; parts of this deviceare broken away for purposes of illustration along the line 3 3 ofFigure 4; and

Figure 4 is a longitudinal sectional view of the device of Figure 3, thesection being taken along the line 4 4 of Figure 3.

It should be borne in mind that although I have shown a preferredembodiment of a system and elements representative of my invention,various other electrical or mechanical expedients for accomplishing theinvention may become apparent to those skilled in the art. Therefore,those details of structure and organization which are presented in thedrawings and described in the speciflcation must be taken asillustrative only, and I do not conceive that my invention is limited tothe use of such particulars.

Structure Referring now to Figure 1 of my drawing, it will be seen thatan embodiment of my invention may comprise a prime mover ID or othersource of mechanical energy, a. power transmission device Il, anelectrical generator i2, and an electronic regulator I3. For purposes ofillustration, I have shown my prime mover to be an aircraft engine, andmy variable power device to comprise a hydraulic transmission. I havealso shown my generator I2 to be separate from and subsidiary to a maingenerator I4, but the provision of a control generator separate from themain generator is purely a matter of choice and the actuating potentialscan be taken from the output of the main generator itself at the will ofthe designer. I have further shown hydraulic transmission I i as beingregulated by a direct current servomotor l5 under the control of theelectronic regulator i3, but the substitution for this particularhydraulic transmission of various equivalents is an obvious expedientand I conceive it to be included in the spirit of my invention,

It will be observed that the various rotary machines are coupled to apair of shafts I6 and I1, shaft I6 connecting the prime mover with thehydraulic transmission, and shaft I1 connecting the hydraulictransmission to the main A. C. generator and the control generator forunitary operation.

Members I8, I2', and I4 may be of any commerclally available design, anddetailed description of their structure and `operation is not necessaryin this specication. Before passing on to a detailed consideration vofthe structure of elements I3 and II, I will set forth briefly the theoryof operation of my invention.

Shaft I6 is driven at a variable speed by prime mover I8. If theelectrical output of member I2, for example the frequency of thealternating current produced thereby, is to be maintained constant, thespeed of rotation of shaft I1 must similarly be maintained constant.Therefore hydraulic transmission II is inserted between shaft I6 andshaft I1, permitting variation in the relative speeds of rotation ofshaft I6 and shaft I1. This variation in power ratio obtainable throughmember II is regulated by the action of servomotor I5 under the controlof electronic regulator I3, which is responsive to variations in acharacteristic of the electrical output of member |2-ln this case tovariations in the frequency of the output. Thus, if the speed of shaftI6 increases over an arbitrarily selected normal speed, the frequency ofthe output of generator I2 increases or tends to increase, and inresponse to this detrimental increase in frequency, regulator I3energizes servomotor I5 to regulate transmission I I in such a manner asto decrease the power ratio between shaft I6 and shaft I1, thusdecreasing the speed of shaft I1 with respect to shaft I6. Similarly, ifthe speed of shaft I6 drops below the selected speed, the frequency ofthe output of generator I2 drops or tends to drop below the intendedfrequency by a small decrement and this causes regulator I3 to energizeservomotor I5 to regulate transmission II in such a manner as toincrease the power ratio between shaft I6 and shaft I1, therebyincreasing the speed of shaft I1 and bringing the frequency back to itsdesired value. The detailed structure bringing about this desired resultwill now be described.

In Figure 2 I have illustrated an electronic reggulator adapted tocomprise a significant portion of my invention. It will be seen that theregulator is comprised of two inter-related portions, a frequencyresponsive portion and a motor control portion 2|. The polarities ofcertain direct current elements are noted, and instantaneous polaritiesof certain alternating current elements are also indicated for readyreference.

,Electrical energy in the form of alternating current of variablefrequency is provided to the regulator by conductors I8 and I9: a switch58 is provided to interrupt the supply of current to the regulator. Onclosing switch 56, electrical energy passes by conductors 1I and 12 toprimary winding 18 of a transformer 24 having a pair of secondarywindings 13 and I8I. Energization of winding 18 induces a potential inthe first secondary winding 13, causing current to flow from winding 13,through conductor 14, a potentiometer 38, conductor 15, a capacitor 25,and conductor 16. A portion of the IR drop in potentiometer 38 producesa current ow through one of a pair "of paths as follows, depending onthe instantaneous polarity of the potentials across the potentiometer.

When the movable contact 18 of potentiometer 38 is positive with respectto its lower terminal, the current flows therefrom through coii-lductors 11 and 88, a rectifier 35, conductors 8| and 82, a resistor 33,conductors 83 and 64, a capacitor 26, conductors 85 and 65, a groundconnection 61, the ground, a secured ground connection 66, a portion ofa grid bias potentiometer 32, conductors 86, 81, and 98, a secondrectifier 31, and conductors 9| and 92 to thev negative lower terminalof potentiometer 38.

When the movable contact 18 of potentiometer 38 is negative with respectto its lower terminal, current flows as follows: from the lower terminalof potentiometer 38 through conductors 92 and 93, a third rectifier 36,conductors 94 and 62, resistor 33, conductors 83 and 84, capacitor 26,conductors 65 and 65, ground connection 61, the ground. groundconnection 66, a portion of potentiometer 32, conductors 86, 81, and 99,a fourth rectifier 38, and conductors and 11 to the negative movablecontact 18 of potentiometer 30.

It will be noted that rectiilers 35, 36, 31, and 38 are connected toform a conventional rectifier bridge. y

The grid 53 of a triode 58 is connected to resistor 33 and capacitor 26by conductor 96. The cathode 52 of triode 58 is connected to capacitor26 and ground connection 61 by conductor 91 and conductor 98. The inputvoltage impressed on triode 58 is therefore the D. C. voltage dropappearing across resistor 33, the rectifier bridge, and the in-circuitportion of potentiometer 32, all in series. In parallel with this dropis a small A. C. ripple drop across condenser 26.

A grid bias battery 45 is connected, by closing a. switch 51, in acircuit as follows: from the positive terminal of the battery throughconductor 1, grid biasing potentiometer 32, conductor 8, switch 51, andconductor I9 back to the negative terminal of the battery.

Cathode 52 of triode 58 is connected to the fixed positive terminal ofgrid bias potentiometer 32 by conductors 91, 98, and 65, groundconnection 61, the ground, and ground connection 66. Grid 53 isconnected to the movable negative terminal of grid bias potentiometer 32by conductor 96, conductor 83, resistor 33, rectifier bridge 39,conductor 81, and conductor 86. Thus, grid 53 is biased negatively by aD. C. voltage dependent upon the position of slider 66.

Energization of winding 18 of transformer 24 also generates potentialsin the second secondary winding I8I of transformer 24, causing currentto flow from winding I8I through conductor |82, a third potentiometer3|, conductor |83, an inductor 28, and conductor |84. A portion of thevoltage drop in potentiometer 3| causes current flow through one of apair of paths 'as follows depending on the instantaneous polarity of thepotentials across the potentiometer.

When the movable contact |85 of potentiometer 3| is positive withrespect to its upper terminal, current flows therefrom throughconductors |86 and |81, a fifth rectifier 42, conductors |88 and III, asecond resistor 34, conductors II2 and II3, a second capacitor 21,conductors ||4 and 65, ground connection 61, the ground, groundconnection 66, the lower portion of potentiometer 32, conductors 86,II5, and II6, a sixth rectifier 44, conductors |I1 and II8, and back tothe upper negative terminal of potentiometer 3|.

When the movable contact of potentiometer 3| is negative with respect toits upper terminal, current flows as follows: from the upper terminal ofpotentiometer 3l through conductors II8 and |2i, aseventh rectifier 4|,conductors |22 and I I, resistor 34, conductors II2 and I|3, capacitor21, conductors I4 and 85, ground connection 51. the ground, groundconnection 88, the lower portion of potentiometer 32, conductors 88, H5,and |23, an eighth rectifier 43, conductors |24 andv |55, and back tothe negative movable contact |85 of potentiometer 3|. l

It will be observed that rectiiiers 4|, 42, 43, and 44 are connected toform a second conventional rectifier bridge.

The grid 83 of a triode 80 is connected to resistor 34 and capacitor 21by conductor |24. The cathode 82 of triode 80 is connected to capacitor21 and ground connection 81 by conductor |25. The input voltageimpressed on triode 60 is therefore the D. C. voltage drop appearingacross resistor 34, the rectifier bridge, and the in-circuit portion ofpotentiometer 32, all in series. In parallel with this drop is a smallA. C. ripple drop across condenser 21.

Cathode 82 of triode-60 is connected to the fixed positive terminal ofgrid bias potentiometer 32 by conductors |25, 88, and 85, groundconnection 61, the ground, and ground connection 66. Grid 53 of triode60 is connected to the movable negative terminal of grid biaspotentiometer 32 by conductors |24 and ||2, resistor 34, conductorrectifier bridge 40, and conductors IIE and 86. This grid 83 is biasednegatively by a D. C. voltage dependent upon the position of slider |05.

Capacitor 25 and potentiometer 30 form a series circuit (A), fed bysecondary winding 13. in which the current is a direct function of thefrequency. Inductor 28 and potentiometer 3| form a second series circuit(B), fed by secondary winding in which the current is an inversefunction of the frequency. Secondary windings 13 and IOI areelectrically identical, as are potentiometers 30 and 3|. Thus for arelatively low frequency, the current in series circuit A may be lessthan that in series circuit B; for a relatively high frequency thecurrent in series circuit A may be greater than that in series circuitB. By properly selecting the circuit constants the device may bearranged so that for a selected frequency the currents in the two seriescircuits are equal. Then by properly adjusting the movable contacts 18and |05 to make up for differences in the impedances of rectifierbridges 39 and 40,

resistors 33 and 34, and capacitors 26 and 21, as well as slightelectrical idiosyncracies in the triodes 50 and 60, all respectively,the signals may be made to have equivalent electrical effect on theoutput currents of triodes 50 and 5|, again respectively.

On closing switch 56, electrical energy also passes by conductors |3|and |32 to the primary winding |30 of a second transformer 22 having asecondary winding |33, and this generates an alternating voltage in thesecondary winding. The output circuit of triode 50 may be traced asfollows: from the upper terminal of winding |33 through conductor |34,the plate 64 of triode 50, the triode, cathode 52, conductor 91,conductor |35, the armature |31 of a direct current motor I having apair of iield windings 46 and 41, conductor |4I, field winding 46,conductor i 42, and back to the other terminal of winding |33. Flow ofcurrent in this output circuit causes rotation of armature |31 in a rstdirection.

On closing switch 58 electrical energy further passes by conductors |43and |44 to the primary winding |39 of a third transformer 23 having vnon Isl.

a secondary winding |45, and this generates ali alternating voltage inthesecondary winding. The output circuit of triode may be traced asiollows: from the upper terminal of winding |45 through conductor |48,plate 84 of triode 53, the triode, cathode 82, conductor |25, conductor|35, armature |31, conductor I4I, field winding 41, conductor |41 andback to the other terminal of winding |45. Windings 48 and 41 are soarranged that currents flowing through them imm conductor I4| cause themotor to rotate in opposite directions.

As previously pointed out, equivalent signals are impressed at the,selected frequency, on the grids of triodes 50 -and 80, causing equalcurrents to flow in the plate circuits. Now by properly adjusting gridbias potentiometer 32, the negative bias on both grids may be increaseduntil both triodes cease to discharge. This will be referred to as thenormal condition of the regulator.

The structure of a hydraulic transmission adapted for use in my systemwill now be described, reference being primarily made to Figures 3 and4. Transmission |I comprises a housing |50 having open ends and acentral parti- Driving shaft I8 passes through an end plate |52 anddriven shaft I1 passes through an end plate |53: the end plates aresecured to the housing in fluid tight relation, and the same relation ismaintained between the end plates and the shafts. Partition |5I divideshousing |50 into a smaller chamber |54 and a larger chamber |55.Passages I 56 and |51 leading from chambers |55 and |54 respectively arearranged to be selectively connected and cut off by the action of avalve I 60 having a p0rt IBI which can be aligned 'with the passages byrotation of the valve about its axis. The valve is provided with anextension shaft |62 passing through a packing gland |83 threadedlyengaging housing |58.

Shaft I8 may be enlarged at its inner end to comprise a pump chamber|10, `a. distribution chamber |1| and a hollow portion |13. Shaft I6passes through an opening |14 in partition I5I and is maintained influid tight bearing re lationship therewith by a locking member |15.Hollow portion |13 communicates with chamber |54 by apertures |16 and|11, and with a pair of passages |80 and |8| leading into pump chamber|10.

Pump chamber |10 is provided with a iiuid tight cover plate |82 throughwhich shaft I1 also passes in iiuid tight rotative relation. Shaft I1 isprovided at its inner end with a gear |83 having a bearing |84 in theinner wall of pump chamber |10. Gear |83 is adapted to cooperate withgears |85 and |86 operating in appropriate recesses in chamber |10 tocomprise a pair of gear pumps, and suitable passages |81 and |83 spacedfrom passages |80 and |8| are provided to give egress from pump chamber|10 into chamber |55.

In use the transmission is filled with fluid and shaft I8 is driven. Ifvalve |60 is closed, no means of fluid passage between chambers |54 and|55 in response to the fluid pump operation is provided, the gears arehydraulically locked, and shaft I1 rotates with shaft I8. If on theother hand, valve |60 is wide open, the fluid pumped by interaction ofthe gears can easily return to chamber |54, gear |83 is not locked withgears |85 and |86, and shaft I1 does not rotate.

For any given speed of rotation of shaft I8,

name

Operation The operation of my system can now be described. Suppose theengine to be operating at a cruising speed of 2,000 R. P. M., at whichspeed generator I4 is designed to produce alternatingcurrent of thedesired frequency, say 400 cycles per second. The generator potential isapplied to the primary of transformer 10, and potential drops appearacross resistors 36 and 3| which are 180 degrees out of phase.Potentials also appear across the rectifier bridges of such polarity asto tend to bring the grids of the triodes to positive potentialscompared with their respective cathodes. 'I'hese rectifier bridgepotentials, however, are opposed by the potentials of the grid biasbattery 45, and the potential difference impressed across each ofcapacitors 26 and 21 is the resultant of a continuous D. C. componentand an opposing pulsating D. C. component derived from the rectifierbridge. This resultant has a wave shape which may be analyzed as a.basic D. C. potential and numerous superimposed A. C. ripple potentialsof various frequencies, including the basic 400 cycles and itsharmonies. To the various A. C. potentials the capacitors presentimpedances of greater or less magnitudes; to the D. C. potentials thecapacitors are non-conducting. 'I'he effect of the capacitors istherefore to shunt out substantially all the A. C. potentials so thatthe potentials impressed upon the grids are substantially pure D. C.potentials.

As previously pointed out, at the desired frequency the currents throughcircuits A and B and therefore the pulsating potentials at the outputsof rectiier bridges 39 and 40 are equal. The magnitude of the biaspotential is adjusted by potentiometer 32 until the resultant equalpotentials on grids 53 and 63 are barely suflicient to prevent the tubesfrom firing. Since the frequency of the generator is that desired, theadjustment of valve |50, which should be in a position midway of itstravel, is such that the resistance to the flow of fluid through thetransmission is suiicient to allow the right amount of relative rotation4between shafts I6 and I1, and there is no necessity for either tube tosupply energy to actuate the motor I to close or open the valve.

Now let the speed of the engine increase to a maximum of, say 3000 R. P.M. This tends to cause the generator to produce 600 cycles A. C., but asthe frequency of the current increases beyond 400 cycles, more currentbegins to ow in series circuit A than in series circuit B. A greaterpositive pulsating potential appears at the terminals of rectifierbridge 39 than that which the grid bias was adjusted to balance. Grid 53therefore goes sufficiently positive to allow triode 50 to fire, andcurrent passes to motor I5 through field winding 46 during each positivehalf cycle of plate 54. This causes the motor to operate, rotating shaft|62 in such a direction as to open valve |60 wider, until the smallerfluid resistance in the fluid transmission reduces the speed of rotationof shaft I1 to the value at which the frequency of generator I4 is againnot desired. This in turn reduces the iiow of current in potentiometerand therefore the positive potential on grid 53, and tube 50 ceasesfiring at the next ensuing end of a positive half cycle.

Since the voltage applied to grid 53 will be greater, the more thefrequency departs from 400 cycles, it will be apparent that the currentflow through tube 50 to motor I5 will increase as the frequency departsfrom the desired value. This is true even where tubes 50 and 60 aregasfilled since an A. C. anode voltage is employed and in such case theoutput of a gas-filled tube varies with the grid voltage. If vacuumtubes were employed for tubes 50 and 60, this variation in currentsupplied to motor I5 would be even greater. Since motor I5, as describedabove, is a D. C. motor, it will be obvious that as the current suppliedto it thus increases, it will tend to run faster and hence adjust thefluid transmission more rapidly, Thus when the frequency has departedsubstantially from the desired value, a more rapid correction isobtained than when the frequency departure is small.

At the time the positive potential of rectifier bridge 39 increases thatof bridge 40 decreases, but as this simply increases the negative biason grid 63 of tube 60, which is not firing, no effective change isbrought about by this potential decrease.

Finally, let the speed of the engine drop to a minimum value of, say1600 R. P. M. This tends to cause the generator to produce 200 cycle A.C., but as the frequency of the current decreases below 400 cycles, morecurrent begins to flow in series circuit B than in series circuit A. Agreater positive pulsating potential appears at the terminals ofrectifier bridge 40 than that which the grid bias is adjusted tobalance. Grid 63 therefore goes suiiiciently positive to allow triode 60to re, and current passes to motor I5 during each positive half cycle ofplate 64. This causes the motor to operate, rotating shaft |62 in such adirection as to close valve |60 tighter, until the greater fluidresistance in the fluid transmission increases the peed of rotation ofshaft I1 to the value at w yich the frequency of generator I4 is againthat desired. This in turn reduces the flow of current in potentiometer3| and the positive potential on grid 63, and tube 60 ceases ring at thenext ensuing end of a positive half cycle. Again, the speed at whichmotor I5 operates to adjust the transmission to correct the frequency isdependent upon how much the frequency drops below the desired value.

At the time the positive potential of rectifier bridge 40 increases,that of bridge 39 decreases, but as this simply increases the negativebias on the grid 53 of triode 50, which is not firing, no effectivechange is brought about by this potential decrease.

It will now be seen that I have disclosed a system for regulating theoutput of an electrodynamic machine whose output varies with its speedof rotation, so that the machine may be driven by a source of powerhaving a variable speed. Substitutions and alterations in my system willbe apparent to those skilled in the art, and therefore I do not wish tobe limited by details of structure which are herein disclosed for thesake of illustration, but only by the subjoined claim.

I claim as my invention:

In a device of the class described, in combination: a rotatable shaft;means driven by said shaft to produce an alternating voltage of whichthe frequency varies with the speed of the shaft;

means for driving said shaft; means variably coupling said driving meansto said shaft; reactive impedance means having an inherentcharacteristic response to current of a selected frequency and giving aresponse to the departure of said frequency from said selected Valuewhich varies in magnitude and direction with the magnitude and directionof said departure; a variable speed electric motor for varying saidcoupling means so as to maintain said frequency at said absolute value;and means for energizing said motor in a direction and to a varyingextent dependent upon the direction and magnitude of the response ofsaid impedance means, said last mentioned means being eiective to causesaid motor to vary said coupling means at a speed dependent upon theamount of departure of said frequency from said selected value.

CHARLES W. EICHHORN.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number Number 10 UNITED STATES PATENTS Name Date Schribner July 7, 1896Robson June 22, 1915 Nyquist Dec. 21, 1926 Macalpine Aug. 4, 1936Heising Nov. 30, 1937 Schmidt May 9, 1939 Ratie Jan. 16, 1940 Koch Feb.13, 1940 Ballou July 8, 1941 Martin July 29, 1941 Brooks Jan. 13, 1942Alexandersson Apr. 14, 1942 Crosby Apr. 21, 1942 Hilferty Nov. 23, 1943Armentrout May 23, 1944 Finison Apr. 16, 1946 Lotts et al. Sept. 21,1948 FOREIGN PATENTS Country Date France Mar. 20. 1914

